Permselective membranes suitable for use in desalination of aqueous solutions are the subject of numerous patents. Cadotte U.S. Pat. No. 4,277,344 discloses permselective multi-layer membranes in which there is a microporous polysulfone substrate layer and a superposed polyamide layer made from an aromatic triacid halide and an aromatic diamine. Scala et al. U.S. Pat. No. 3,744,642 discloses multilayer membranes in which one layer is porous substrate and the juxtaposed layer is a polyamide, a polyphenylester, or a polysulfonamide. Weyland et al. U.S. Pat. No. 3,649,687 discloses the use of 1,3,5-cyclohexane tricarbonyl chloride in the production of crosslinking agent: 1,3,5-cyclohexane triisocyanate. U.S. Pat. Nos. 4,520,044 and 4,529,646 disclose permselective multilayer membranes in which there is a microporous polysulfone support and a polyamide layer made using 1,3,5-cyclohexane tricarbonyl chloride and a diamine.
U.S. Pat. No. 4,626,468 discloses permselective multilayer membranes in which there is a microporous polysulfone support and a polyamide layer made from meta-phenylenediamine and based on polymerized acid chloride present from 10 to 80 weight percent repeating units derived from trimesoyl chloride, 90 to 15 weight percent repeating units derived from cyclohexane-1,3,5-tricarbonyl chloride and up to 40 weight percent repeating units derived from isophthaloyl chloride, terephthaloyl chloride or mixtures thereof.
U.S. Pat. No. 4,783,346 discloses a multistage process for preparing interfacially polymerized polyamide reverse osmosis membranes on a microporous support. The process involves first applying a solution containing from 1 to 10 wt % of an aromatic diamine having 1 or 2 rings and then a solution of a mixture of acyl chlorides having a combined average per acyl chloride containing molecule of 2.2 to 4 acyl chloride groups in a solvent immiscible with the first solvent applied to the microporous substrate. Then a solution of different acyl chlorides is applied to the substrate. The individual acyl chlorides in this second solution can have 2.2 to 4 acyl chloride groups attached to an alkylene aliphatic group of 4 to 12 carbon atoms or an aromatic or cycloaliphatic group having 1 or 2 rings and containing 6 to 14 carbon atoms.
U.S. Pat. No. 4,643,829 discloses a multilayer membrane for performing reverse osmosis comprising a porous support and a layer formed of poly(meta-phenylenecyclohexane-1,3,5-tricarboxamide).